KR20120035873A - Image processing apparatus, image processing method, inkjet printing apparatus, and inkjet printing method - Google Patents

Abstract

PURPOSE: An image processor, an image processing method, an inkjet printer, and an inkjet printing method is provided to correct image data for reducing a picture degradation caused by a deviation of a discharge performance of a nozzle. CONSTITUTION: An inkjet printing method comprises a correction unit. The correction unit sets input image data corresponding to a nozzle region as a processing block. The nozzle region is set inside of a nozzle array along an arrangement direction of the nozzle and composed of a plurality of nozzles. The correction unit corrects the input image data according to a parameter set with respect to each processing block. The nozzle region corresponding to the input image data of the processing block is set according to a position of a boundary between an overlap portion(C_T) and non-overlap portion(C_A1) with respect to a print head(102).

Description

Image processing apparatus, image processing method, inkjet printing apparatus, and inkjet printing method {IMAGE PROCESSING APPARATUS, IMAGE PROCESSING METHOD, INKJET PRINTING APPARATUS, AND INKJET PRINTING METHOD}

The present invention relates to an inkjet printing apparatus for printing an image using printheads in which a plurality of chips provided with a plurality of ink ejection nozzles are arranged along the arrangement direction of the nozzle, and an image processing apparatus for processing data used by the same. will be.

In the inkjet printing apparatus, printheads arranged in a predetermined direction and having ejection portions (hereinafter, these ejection portions are referred to as nozzles) composed of inkjet printing elements, ejection ports, and fluid passages communicating therewith are used. do. As an inkjet printing apparatus, a so-called full-line type inkjet printing apparatus, which fixes the printheads to the main body of the printing apparatus and performs printing operations by conveying the print media in a direction crossing the long sides of the printhead. inkjet printing apparatuses are known. The full-line type inkjet printing apparatus can form an image at a high speed over the entirety of the print medium by continuously conveying the print medium while printing one line image portions collectively in the long print heads.

As the print heads of such a full-line type inkjet printing apparatus, so-called couple heads, which are made long by arranging a plurality of long chips that can be manufactured relatively inexpensively with high precision, are used (see Japanese Laid-Open Patent Publication No. 2006-264152). ). Realizing color image formation using such coupling heads is performed by black (K), cyan (C), magenta (M), and yellow (Y), respectively. This is possible by arranging a plurality of mating heads corresponding to inks having different colors.

Print heads used in an inkjet type printing apparatus have a discharge amount variation between a plurality of nozzles due to manufacturing error or the like. If there is such a deviation in the discharge amount, density unevenness is likely to occur in the printed image.

Conventionally, it is known to use a head shading (HS) technique such as that disclosed in Japanese Laid-Open Patent Publication No. Hei 10-13674 (1998) as a treatment for reducing such concentration unevenness. The head shading technique corrects image data in accordance with information on the discharge amount of each nozzle. By this correction, the number of ink dots finally printed can be increased or decreased, and the density in the print image can be adjusted.

However, when the head shading technique as disclosed in Japanese Laid-Open Patent Publication No. Hei 10-13674 (1998) is applied to a long print head having a large number of nozzles, since the image data processing is performed at individual nozzles, The problem arises that it takes a lot of time. In addition, when correcting an image using a head shading technique, a large memory capacity is required, resulting in an increase in cost. In addition, with the higher resolution of the nozzles of the print head, the detection device for detecting the discharge amount of each nozzle is also required to be high resolution, which also increases the device cost.

An object of the present invention is to enable image data correction in an inkjet printing apparatus to reduce image deterioration caused by variation in ejection performance of a nozzle while suppressing an increase in required memory and processing time.

To provide a solution to the above problem, certain aspects of the present invention include the following features.

A first aspect of the invention relates to print data generated in response to input image data using one or more print heads provided with a plurality of chips each having one or more nozzle arrays including a plurality of nozzles for ejecting ink. An inkjet printing apparatus for printing images on a print medium by ejecting ink from nozzles on the basis of the ink, wherein the nozzle array of the chip has an overlap portion and a non-overlap portion, and a print area printed by the overlap portion of the nozzle array of the chip. And the print area printed by the overlapping portion of the nozzle array of the chip adjacent to the chip overlap, and the non-overlap portion of the print area printed by the non-overlap portion of the nozzle array of the chip and the nozzle array of the chip adjacent to the chip. The print area printed by the ink does not overlap, and the inkjet printing apparatus Setting input image data corresponding to nozzle regions defined in the nozzle arrays and configured by a plurality of nozzles, respectively, along the direction in which the nozzles are arranged, as processing blocks, and according to the parameters defined for each of the processing blocks. A correction unit for correcting the input image data, wherein the nozzle regions corresponding to the input image data of the processing blocks are defined according to positions of boundaries of the overlap portions and the non-overlap portions in the print head. do.

A second aspect of the invention provides an image processing input image data for printing using one or more print heads provided with a plurality of chips each having one or more nozzle arrays including a plurality of nozzles for ejecting ink. A processing method, wherein the nozzle array of the chip has an overlap portion and a non-overlap portion, and a print area printed by the overlap portion of the nozzle array of the chip and a print printed by the overlap portion of the nozzle array of the chip proximate to the chip. The area overlaps, and the print area printed by the non-overlap part of the nozzle array of the chip and the print area printed by the non-overlap part of the nozzle array of the chip adjacent to the chip do not overlap, and the image processing method includes: A plurality of nozzles defined within the nozzle arrays along the arrangement direction of the nozzles A setting step of setting the input image data corresponding to the nozzle areas to be configured as the processing blocks, and a correcting step of correcting the input image data according to the parameters determined for each of the processing blocks by the setting step; The setting step is defined in accordance with the positions of the nozzle areas corresponding to the input image data of the processing blocks, the positions of the boundaries of the overlapping portions and the non-overlaping portions in the print head.

According to the present invention, it is possible to suppress an increase in required memory and processing time, and to correct image data that reduces image deterioration caused by variation in ejection performance of a nozzle in an inkjet printing apparatus.

Other features of the present invention will become apparent from the following description of the preferred embodiments (with reference to the accompanying drawings).

1 is a diagram schematically showing an inkjet printing apparatus of a first embodiment of the present invention.
2 is a block diagram illustrating a printing system according to an embodiment of the present invention.
3 is a block diagram showing the configuration of an image processing unit in the inkjet printer of the first embodiment of the present invention.
4A and 4B are explanatory diagrams showing the configuration of print heads used in the first embodiment.
5A to 5C are diagrams showing nozzle utilization rates of overlapping portions and non-overlaping portions of the print heads shown in FIGS. 4A and 4B.
6 is a view for explaining the visibility.
7A to 7E are diagrams showing luminance in overlapping portions and non-overlap portions of the print heads shown in FIGS. 4A and 4B.
8A and 8B are diagrams showing detection patterns in the first embodiment.
9A and 9B are flowcharts showing HS processing.
10A and 10B are flowcharts illustrating multicolor shading (MCS) processing.
11 is an explanatory diagram showing a configuration of print heads used in the second embodiment.
12A to 12C are diagrams showing luminance in overlap portions and non-overlap portions of the print heads in the second embodiment.
13 is a diagram for explaining processing blocks in the fifth embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 is a diagram schematically showing a printer of an inkjet printing apparatus of a first embodiment of the present invention. As shown in FIG. 1, the printer 100 has print heads 101 to 104 provided on a frame forming the structural member of the printer. That is, each of the print heads 101 to 104 is arranged along a predetermined direction at a distance corresponding to the width of the print paper 106, such that cyan (C), magenta (M), yellow (Y), and black (K). It is a so-called full-line type apparatus which has a some nozzle which discharges the some ink of (). The nozzles of each nozzle array are arranged at a resolution of 1200 dpi. The printer 100 is also provided with a scanner (color information acquiring means) 107 which acquires color information about images printed by the print heads 101 to 104 in parallel with the print head 104. The scanner 107 in the embodiments has a resolution of 1200 dpi.

The print paper 106 functioning as a print medium is conveyed in the direction of the arrow in the drawing by the conveying roller 105 (and other rollers not shown) being rotated by the driving force of a motor (not shown). While the print paper 106 is being conveyed, ink is ejected from the plurality of nozzles of each of the print heads 101 to 104 in accordance with the print data, whereby one raster images corresponding to the nozzle arrays of the respective print heads are sequentially printed. do. Thus, by repeating the ink ejection operation from each of the print heads for the conveyed print paper, for example, one page of image can be printed. Note that the printing devices to which the present invention can be applied are not limited to the full-line type devices as described above. As is apparent from the following description, the present invention can also be applied to a so-called serial line type printing apparatus which performs printing by scanning a print head in a direction intersecting a conveyance direction of print paper, for example.

2 is a block diagram illustrating a printing system according to an embodiment of the present invention.

As shown in the figure, the printing system is configured to have the printer 100 shown in FIG. 1 and a personal computer (PC) 300 functioning as its host apparatus.

The host PC 300 is configured to have the components described below as main components. The CPU 301 executes the processing described below in accordance with programs stored in the HDD 303 or the RAM 302 serving as a storage unit. For example, the CPU functions as a conversion data generation unit and a switching unit that execute the conversion data generation step, table switching step, and the like, which will be described later. The RAM 302 is volatile storage and temporarily stores a program or data. The HDD 303 is a nonvolatile storage and likewise stores programs and data. The data transmission I / F (interface) 304 controls the transmission and reception of data with the printer 100. As a connection method of data transmission and reception, USB, IEEE1394, LAN, etc. can be used. The keyboard / mouse I / F 305 is an I / F that controls human interface devices (HIDs) such as a keyboard and a mouse. The user can provide input through this I / F. Display I / F 306 controls what is shown on the display (not shown). The scanner controller 317 controls the driving of the above-described scanner 107 based on the control signal from the CPU 311.

On the other hand, the printer 100 is configured to have the components described below as main components. The CPU 311 executes the processing of each of the embodiments described later in FIG. 3 according to the programs stored in the ROM 313 and the RAM 312. The RAM 312 is volatile storage and temporarily stores programs and data. ROM 313 is non-volatile storage, which may store table data generated by the processes of each of the embodiments described later in FIG. 3.

The data transmission I / F 314 controls the transmission and reception of data with the PC 300. The head controller 315 supplies print data to each of the print heads 101 to 104 shown in FIG. 1 and also controls the ejection operation of the print heads. Specifically, the head controller 315 may be configured to read control parameters and print data from a predetermined address of the RAM 312. When the CPU 311 writes the control parameters and the print data to the predetermined address of the RAM 312, the process is started by the head controller 315, and ink ejection from the print head is performed. The image processing accelerator 316 is made of hardware and executes image processing at a higher speed than the CPU 311. Specifically, the image processing accelerator 316 may be configured to read parameters and data necessary for image processing from a predetermined address of the RAM 312. When the CPU 311 writes parameters and data to the predetermined address of the RAM 312, the image processing accelerator 316 is started to perform predetermined image processing. In the embodiments, the processes of generating table parameters (converted data) used in the MCS processing unit described later in each of the embodiments subsequent to FIGS. 4A and 4B are performed by software in the CPU 311. On the other hand, the print image processing including the processing of the MCS processing unit is performed by the hardware processing in the image processing accelerator 316. Note that the image processing accelerator 316 is not necessarily required. Depending on the specification of the printer, the generation process and the image processing of the above table parameters may be executed only by the CPU 311.

<First Embodiment>

3 is a block diagram showing the configuration of an image processing unit in the inkjet printer of the first embodiment of the present invention. In this embodiment, each component for the control and processing of the printer 100 shown in FIG. 2 constitutes an image processing unit. Note that the application of the present invention is not limited to this configuration. For example, an image processing unit may be disposed in the PC 300 shown in FIG. 2, or a portion of the image processing unit may be disposed in the PC 300 and the remaining portion may be disposed in the printer 100.

As shown in FIG. 3, the input unit 401 outputs the image data received from the host PC 300 to the image processing unit 402. The image processing unit 402 includes an input color conversion processing unit 403, an MCS processing unit 404, an ink color conversion processing unit 405, an HS processing unit 406, a TRC processing unit 407, and a quantization processing unit. Configured to have 408.

In the image processing unit 402, first, the input color conversion processing unit 403 converts the input image data received from the input unit 401 into image data corresponding to the color reproduction range of the printer. In the present embodiment, the input image data is data indicating color coordinates (R, G, B) of a color space coordinate system such as sRGB, which is a color expressed by the monitor. The input color conversion processing unit 403 converts the input image data R, G, and B data composed of 8 bits into a color signal composed of three elements, for example, by a known processing technique using a three-dimensional LUT. Each 10-bit image data R ', G', and B 'data ("10-bit R', G ', and B' color signal image data") within the color reproduction range are converted into image data. In this embodiment, a three-dimensional lookup table (LUT) is used, and the conversion process is performed using an interpolation operation according to the LUT. Note that in the present embodiment, the resolution of the image data handled by the image processing unit 402 is 600 dpi and the resolution of the output unit 409 is 1200 dpi as described later.

The MCS (multicolor shading) processing unit 404 performs the conversion operation of correcting the color difference with respect to the image data converted by the input color conversion processing unit 403 as the first conversion means of this embodiment. This process is also executed using a conversion table (parameter generating means) including a three-dimensional lookup table. According to this conversion process, even when there is a variation in ejection performance between nozzles for printing the same area of the print head in the output unit 409, the color difference caused by the single ink color or the plurality of ink colors generated thereby is eliminated. Can be reduced. In this embodiment, it is converted into 12-bit device color image data, which is a color signal composed of three elements, by techniques such as well-known matrix calculation processing and three-dimensional lookup table processing.

The ink color conversion processing unit 405 uses R, G and B image data of each of 12 bits processed by the MCS processing unit 404 as a second conversion means of the present embodiment, and is used by a printer to generate color of ink. The image data is composed of signal data. Since the printer 100 of this embodiment uses ink of cyan (C), magenta (M), yellow (Y), and black (K), the image data of the RGB signal is each 14-bit C, M, Y. And image data (" 14-bit CMYK color signal image data ") consisting of color signals including and K data. This color conversion processing is also performed using an interpolation operation together with the three-dimensional lookup table, similarly to the above-described input color conversion processing unit. Note that as another conversion method, matrix operation processing and the like can be used in the same manner as described above.

By inputting image data corresponding to an ink color signal, the HS (head shading) processing unit 406 generates 14 bit data for each ink color in accordance with the respective discharge amounts of the plurality of nozzles constituting the print heads. 16-bit ink color signal is converted into image data. In other words, the HS processing unit 406 performs the same processing as the conventional head shading processing. In this embodiment, processing is performed using the one-dimensional lookup table.

The TRC (Tone Reproduction Curve) processing unit 407 uses 16 bits in which HS processing has been performed to adjust the number of dots printed at the output unit 409 for each ink color. The ink color signal image data is corrected. Generally, there is no linear relationship between the number of dots printed on a print medium and the optical density of the print medium obtained by the number of dots. Therefore, the TRC processing unit 407 adjusts the number of dots printed on the print medium by correcting each 16-bit image data with 18-bit image data to create a linear relationship. Specifically, this processing is performed using a one-dimensional lookup table.

The quantization processing unit 408 performs quantization processing on the 18-bit ink color image data processed by the TRC processing unit 407, where one bit represents two prints and one zero represents nonprinting. Generate value data. Note that in applying the present invention, the form of quantization is not particularly limited. For example, 8-bit image data can be directly converted into binary data (dot data), or a few bits of multi-value data can be quantized once and finally converted into binary data. have. The quantization processing method may adopt an error diffusion method and may also employ a pseudo halftone process such as a dithering method.

The output unit 409 drives the print head based on the binary data (dot data) obtained by quantization to perform printing by ejecting ink of each color onto the print medium. In this embodiment, the output unit includes a print mechanism provided with the print heads 101 to 104 shown in FIG.

Next, the print heads 101 to 104 used in this embodiment will be described with reference to Figs. 4A and 4B. The print heads 101 to 104 in this embodiment are configured to connect all the nozzle arrays of the plurality of chips to each other by connecting respective chips having at least one nozzle array in which the plurality of nozzles are aligned. . Here, the configuration of the cyan ink ejecting print head 102 of FIGS. 4A and 4B will be described as an example. The head chips C_CH0 and C_CH1 are configured so that, from their respective ends, certain areas C_T (overlap portions) overlap each other in a direction orthogonal to the nozzle. That is, the overlapping portion of the head chip C_CH0 and the overlapping portion of the head chip C_CH1 are arranged to be at the same position along the long side direction (x direction) of the print head 102. However, adjacent head chips are at positions deviated in the y direction and are arranged in a zigzag shape as a whole. Regions C_A0 and C_A1 shown in FIGS. 4A and 4B are non-overlap portions that are portions other than overlap portions in the chip. Note that the above configuration is the same for the other print heads 101, 103, 104.

The number of nozzles per unit length in the x direction of the overlap part C_T is larger than the number of nozzles per unit length in the x direction of the non-overlap part C_A0 and the non-overlap part C_A1. For this reason, when the nozzle usage rate in a non-overlap part and the nozzle usage rate in an overlap part are the same, the number of dots per unit area printed by the overlap parts will be larger than the number of dots per unit area printed by the non-overlap part. As a result, the density of the images printed by the non-overlap portions is lower than the density of the images printed by the overlap portions. Thus, as shown in Figs. 5A to 5C, the nozzle utilization rate is different between the overlapping portions and the non-overlapping portions. FIG. 5A illustrates an example in which the nozzle utilization rate (shown in solid line) of C_CH0 is converted to the nozzle utilization rate (shown in dashed line) of C_CH1 in the overlapping portions of the chips shown in FIG. 4A. FIG. 5B illustrates an example in which the nozzle usage rate (shown in solid line) of C_CH0 and the nozzle usage rate (shown in dashed line) of the connected C_CH1 cross each other in the overlap portion. 5C illustrates an example in which the nozzle usage rate (shown in solid line) of C_CH0 and the nozzle usage rate (shown in dashed line) of the connected C_CH1 cross several times in the overlap portion. Note that the nozzle utilization rate of the overlap portion is not limited to the example shown in FIGS. 5A to 5C, and may be set to other usage rates.

Next, a description will be given of the reduction of color unevenness due to manufacturing variation of the print head.

In general, in the HS process, the discharge amount for each nozzle is detected, and the image data correction process is performed based on the detection result. Therefore, in the case of a long head which has a nozzle resolution of 1200 dpi and is associated with A4 (short side 210 mm) printing, the number of nozzles becomes 9900 or more. For this reason, high specifications are required for processing speed and memory. Halftone line images with 1200 dpi resolution have 600 halftone lines per inch, and with the visibility shown in FIG. 6, it is difficult to recognize color unevenness in such images. Halftone lines are lines that vary in thickness and number of lines per unit area, thereby being used to change the density of an image.

Regarding the purpose of reducing density unevenness, applying the HS process and the MCS process per nozzle makes the printing apparatus over-specified when the print head becomes high resolution. Therefore, it is preferable that the processing block of the image data to which the HS processing and the MCS processing are applied is not the pixel data corresponding to each nozzle but the image data corresponding to the nozzle area including a plurality of nozzles.

Next, a description will be given of setting processing blocks ideal for correction processing for improving an image, such as HS processing and MCS processing. As described above, the print heads shown in FIG. 1 are configured such that a plurality of chips are connected and include overlap portions and non-overlap portions.

Manufacturing variations are more common between different chips than within the same chip. Therefore, color unevenness caused in the image caused by manufacturing variation of the print head is more easily recognized by the area printed by the overlap portion composed of the plurality of chips than the area printed by the non-overlap portion.

7A to 7E show the difference in luminance in an image caused by manufacturing variation in the case where the nozzle number of each chip of the print head shown in FIG. 4A is set to 512 and the nozzle number of the overlapping part is set to 128. Shows the presence of. As shown in C_A0 in FIG. 4A, the number of nozzles of the non-overlapped portion when only one end of the chip is an overlap portion is 384, and the number of nozzles of the non-overlapped portion when both ends of the chip are overlapped portions, such as C_A1, is 256. Note that is set up. Also, for convenience of explanation, the discharge amount of the chip CH0 is made smaller than the discharge amount of the chip CH1, and the discharge amount of the nozzles in the chips of each of the chips C_CH0 and C_CH1 are made uniform. In addition, the nozzle usage rates are such that the nozzle usage rate of the chip C_CH0 and the nozzle usage rate of the chip C_CH1 intersect once, as shown in FIG. 5B.

7A shows a case where HS processing and MCS processing are not applied. 7B shows a case where the HS process and the MCS process are applied at 80 nozzle intervals. FIG. 7C illustrates a case where the HS process and the MCS process are applied at intervals of 64 nozzles, which is a common divisor of the nozzle number 128 of the overlap part C_T, the nozzle number 384 of the non-overlap part C_A0, and the nozzle number 256 of the non-overlap part C_A1. . FIG. 7D shows a case where the HS process and the MCS process are applied at 40 nozzle intervals which are the number of nozzles of the overlap part. FIG. 7E illustrates a case where the HS process and the MCS process are applied at 32 nozzle intervals, which is a common divisor of the nozzle number 128 of the overlap part C_T, the nozzle number 384 of the non-overlap part C_A0, and the nozzle number 256 of the non-overlap part C_A1. . In the present embodiment, the number of nozzles in FIGS. 7A to 7E can be easily understood for convenience of drawing, but the present invention is not limited thereto.

As shown in Figs. 7B and 7D, when the number of nozzles in the nozzle area corresponding to the processing block of the HS process and the MCS process is a number other than the common factor of the overlap part and the non-overlap part, the correction of the non-overlap part is relatively a manufacturing deviation. Is affected by a large overlap. On the other hand, as shown in Figs. 7C and 7E, when the number of nozzles in the nozzle area corresponding to the processing block of the HS processing and the MCS processing is made the divisor of the number of nozzles of the overlap portion and the number of nozzles of the non-overlap portion, The influence of the cross section is reduced so that the non-overlap portion can be corrected. By adjusting the number of nozzles in the nozzle area corresponding to the processing block of the HS processing and the MCS processing to be the divisor of the number of nozzles of the overlapping portion and the number of nozzles of the non-overlaping portion, correction suitable for the color difference between the overlapping portion and the non-overlaping portion is performed. It can be carried out. Depending on the degree of color difference caused by manufacturing variations in the overlap and non-overlap portions, it is effective to adopt the least processing block among the common factors for each of the HS processing and the MCS processing to increase the effect on visual recognition. Note that

There are cases where variations occur due to manufacturing variations in the number of nozzles of the overlapping portion and the number of nozzles of the non-overlap portion, and a misalignment occurs between the overlapping portion and the non-overlap portion between the heads of different colors. In this case, the overlap portion and the non-overlap portion exist in the nozzle area corresponding to one processing block. Here, if the influence of the overlap portion on the non-overlap portion cannot be visually recognized, no change of processing block is necessary. However, in the case where the influence of the overlap portion on the non-overlap portion can be visually recognized, an area having a smaller number of nozzles, which is not visually recognized, among the common factors of the number of nozzles of the overlap portion and the number of nozzles of the non-overlap portion Should be adopted as the nozzle area corresponding to the processing block.

In the present embodiment, for convenience of drawing, it has been explained with the number of nozzles of FIGS. 7A to 7E which can be easily understood, but it should be noted that, as described above, it is also effective to make the processing block a smaller number of nozzles. In the case of the head configuration of this embodiment, HS processing is a common divisor of the nozzle number 128 of the overlap part C_T, the nozzle number 384 of the non-overlap part C_A0, and the nozzle number 256 of the non-overlap part C_A1, for example, at eight nozzle intervals. It is very advantageous to apply the MCS treatment.

Next, the setup of the processing blocks of the HS processing and the MCS processing will be described. 8A and 8B show a pattern for detecting color unevenness caused by manufacturing deviation of the head. The pattern 900 shown in FIG. 8A is a pattern of primary colors (eg, C (cyan), M (magenta), and Y (yellow)). The pattern 910 shown in FIG. 8B includes not only a primary color but also a pattern of secondary colors or more (eg, R (red), G (green), and B (blue)) using a plurality of inks. do. 901 is a pattern for detecting a processing block. Here, it demonstrates using the example of the process block of the eight nozzle which is a good example mentioned above.

Process block detection patterns 901 and 911 have eight nozzles of 1200 dpi wide. The processing block detection patterns 901 and 911 are light and light patterns in which light and shade are alternated at intervals of a width W. These light and dark patterns are read by the scanner 107 or the color measurement device, and the width W is detected. The processing block P is detected using the processing block detection patterns 901 and 911, and the detection region 902 and the second or more color patterns of the primary color pattern 900 corresponding to the width W of the processing block P ( The detection area 912 of 910 is read by a scanner or a color measurement device. According to the read result, the processing contents for the HS processing and the MCS processing described later are set for each processing block P. FIG.

9A is a flowchart illustrating a process s1010 for generating HS processing parameters used in the HS processing unit 406 shown in FIG. This process includes each of steps S1011 to s1014. 9B is a flowchart showing the HS execution process s1020, which includes steps S1021 and s1022.

First, the processing flow of the HS processing parameter generating process s1010 will be described. In step S1011, the pattern of Fig. 9A is printed on the print medium. The image processing performed at the time of pattern printing is the same, and there is no change of parameters depending on the print position. In step S1012, the printed pattern is read by the scanner 107 or the color measurement device. In the following, an example of reading the RGB value as the color information by the scanner 107 will be described. Here, since the processing block is eight nozzles of 1200 dpi, the reading is performed at a high resolution of eight nozzles of 1200 dpi or more. In step S1013, the processing block detection pattern is detected from the result read in step S1012, and eight nozzle areas of the primary color pattern are set. In step S1014, an appropriate one-dimensional lookup table is selected from among the plurality of one-dimensional lookup tables for HS processing, which are provided in advance, according to the RGB values of the previously set area. The selection of this one-dimensional lookup table is performed using a previously provided table that correlates the difference between the target RGB value and the RGB value read by the scanner and the one-dimensional lookup table. The above-described setting of the area of the eight nozzle intervals and selection of the one-dimensional lookup table are performed over the width of the long head.

Next, the operation of the HS process execution process S1020 will be described. In step S1021, it is detected to which processing block the pixels to be processed correspond. Here, when the resolution of the input pixels is 600 dpi, one input pixel corresponds to two output pixels at 1200 dpi. Therefore, the processing block is detected so that the processing resumes at data intervals of four input pixels. In step S1022, the selected one-dimensional lookup table is applied to the input image data to be processed for the detected processing block. The detection of the processing block corresponding to the input pixel to be processed and the application of the one-dimensional lookup table are performed on both the input image data.

FIG. 10A is a flowchart showing a process S1110 for generating MCS processing parameters used in the MCS processing unit 404 shown in FIG. 3, which process includes the operations of steps S1111 to S1114. 10B is a flowchart showing the MCS processing execution process S1120, which includes steps S1121 and S1122.

First, the process flow of MCS process parameter generation process S1110 is demonstrated. In step S1111, the pattern shown in Fig. 9B is printed on the print medium. In the processing carried out when this pattern is printed, the image data processed by the input color conversion processing unit 403 passes through the ink color conversion processing unit 405 through the bypass path shown by the broken line 410 in FIG. Is entered. In this case, therefore, MCS processing is not executed. In step S1112, the RGB value of the pattern printed in step S1111 is read by the scanner 107. Here, since the processing block is eight nozzles of 1200 dpi, the reading is performed at a high resolution of eight nozzles of 1200 dpi or more. In step S1113, the processing block detection pattern is detected from the read result, and eight nozzle areas are set for the primary color pattern or the secondary or higher color pattern. In step S1114, a three-dimensional lookup table used for MCS processing is generated according to the RGB value of the preset area, for example, in the following manner.

First, the pattern colors Rp, Gp, and Bp close to the target colors Rt, Gt, and Bt of the input device colors Rd, Gd, and Bd of the three-dimensional lookup table of the MCS process are estimated based on the read RGB values. Next, the device colors Rn, Gn, and Bn corresponding to the estimated pattern colors Rp, Gp, and Bp are estimated. The target color is, for example, an RGB value (value read by the scanner) of the pattern color corresponding to the device colors Rd, Gd, and Bd when the discharge amount is printed by the print head which is the reference value. And when printing a pattern, the table which converts the device color Rd, Gd, and Bd input into the input color conversion processing unit 403 of FIG. 3 into Rn, Gn, and Bn is produced | generated. By implementing this conversion table for a plurality of patterns, a three-dimensional lookup table of MCS processing is generated. The nozzle area setting at 8 nozzle intervals and the generation of the three-dimensional lookup table are performed over the width of the long head.

Next, the operation of the MCS processing execution process S1120 shown in FIG. 10B will be described. In step S1121, it is detected to which processing block the pixels to be processed correspond. Here, when the resolution of the input pixels is 600 dpi, one input pixel corresponds to two output pixels at 1200 dpi. Thus, the processing block is detected so that the MCS processing can be switched at four input pixel intervals. In step S1122, the three-dimensional lookup table generated for the detected processing block is applied to the input pixel image data to be processed. The application of this three-dimensional lookup table is carried out in an amount corresponding to the input pixels.

As described above, in this first embodiment, image data corresponding to a nozzle area having a common divisor of the number of nozzles in the overlap portion and the number of nozzles in the non-overlap portion is set as a processing block, and then HS processing and MCS processing are performed. Run Accordingly, the boundaries of the nozzle regions corresponding to the input image data of the processing block are set to coincide with the boundaries between the overlapping portions and the non-overlap portions. For this reason, the nozzle which belongs to an overlap part and the nozzle which belongs to a non-overlap part do not mix in one process block, and the influence of the overlap part which affects a non-overlap part also disappears. For this reason, it is possible to reduce image degradation caused by color difference such as color unevenness or density unevenness caused by manufacturing variation. In addition, if there is no change in the length of the head, when the print head becomes high resolution, there is no change in the number of processing blocks for switching parameters, so that an increase in load and cost required for image processing can be suppressed. In addition, even when the print head becomes high resolution, it is not necessary to make the detection device such as a scanner high resolution. That is, color differences caused by manufacturing variations can be reduced regardless of the resolution of the print head.

Second Embodiment

Next, a second embodiment of the present invention will be described.

Fig. 11 is a view showing print heads 501 to 504 used in the second embodiment, which are different from the print heads used in the above-described first embodiment shown in Figs. 4A and 4B. It is different in the same point. That is, the print heads used in the first embodiment described above are the same along the arrangement direction (x direction) of the nozzle so that the overlap portions of the print heads of each color overlap in the conveying direction (y direction) of the print medium. Present at the location). In contrast, the print heads of the second embodiment are arranged so that the overlap portions K_T, C_T, M_T, and Y_T of the print heads of each color do not overlap in the conveying direction (y direction) of the print medium, as shown in FIG. Has a configuration that is arranged.

Now, in each of the print heads shown in Fig. 11, the resolution of the nozzle is 1200 dpi, the number of nozzles of each chip is 704, the number of nozzles of the overlapping portion is 128, and the nozzle of the portion located between the overlapping portions of the print heads of adjacent different colors. The number is 16. The portion located between the overlap portions of print heads of adjacent different colors is called an "offset portion". Here, based on the K head, in the same manner as in FIG. 7C of the first embodiment, if the HS process is performed at 64 nozzle intervals, an image printed by the K head, that is, a black and white image, is shown in FIG. 12A. As shown, the effect of reducing color difference (concentration unevenness) is exhibited as in the first embodiment.

In contrast, for other heads, as shown in FIG. 12B, there is a case where the MCS processing block is set to include both the overlap portion and the non-overlap portion. According to this, the correction effect of color nonuniformity may be reduced. That is, in the print head shown in Fig. 12B, when the process block of the MCS process is 64 nozzles in the same manner as in Fig. 7C of the first embodiment, cyan (C), magenta (M), and yellow (Y) The above-described offset portion exists between the overlap portions of each print head. For this reason, when forming a multicolored image using a plurality of print heads, there may be a case where both overlap portions and non-overlap portions are included in the processing block of MCS processing of the plurality of print heads used for forming the image. In this case, correction processing is performed on the offset data existing in the same processing block and the image data of the image formed by other parts in the same processing block with the same correction value (parameter). For this reason, as in the above-described first embodiment, there is a possibility that the color nonuniformity reduction effect is lowered as compared with the case where MCS processing is performed differently while switching between the overlapping portion and the non-overlaping portion. Fig. 12B shows this state, and in the figures, portions marked by V1 and V2 represent portions in which MCS processing is not properly performed.

Therefore, in the second embodiment, 16 nozzles, which is a common divisor of the nozzle number 128 of the overlap part and the nozzle number 16 of the offset part, are set as the nozzle area corresponding to the processing block. Thus, similarly to the first embodiment, in response to the switching between the images printed by the overlapping portions and the processed images printed by the non-overlaping portions, the processing blocks can be switched and each image data is otherwise differently corrected. can do. 12C shows an example of the state of the correction process performed in the second embodiment. In the present embodiment, the number of nozzles in FIGS. 12A to 12C is easily understood for convenience of drawing, but the present invention is not limited thereto.

Since the HS processing correction can be processed for individual colors, it is also effective to set image data corresponding to a nozzle area having a common divisor of the number of nozzles of overlap portions of each of the print heads and the number of nozzles of non-overlap portions as a processing block. Note that On the other hand, MCS processing uses image data of an image formed by a plurality of color inks. For this reason, the nozzle number of the offset part which is a part between overlap parts of adjacent print heads, and the nozzle number which is a common factor of the nozzle number of an overlap part as mentioned above are set as a nozzle area, and image data corresponding to this nozzle area is processed. It is valid to make a block.

Depending on the degree of color difference caused by manufacturing variations in the overlap and non-overlap and offset portions, the processing block, which is the minimum of the common factors, is increased for the HS and MCS processing to increase the effect on visual recognition. Note that adoption is valid. Further, depending on the number of nozzles of overlap portions and the number of nozzles of non-overlap portions in each of the print heads shown in FIG. 11, positional shift due to variations in manufacturing may occur. In this case, the effect of reducing color unevenness can be increased by adopting the minimum value among the common factors mentioned above.

In the present embodiment, for the sake of convenience of drawing, it has been explained with the number of nozzles of FIGS. 7A to 7E which can be easily understood, but it is noted that it is effective to make the processing block smaller nozzle number as described above. In the case of the head configuration of this embodiment, it is very advantageous to apply the HS process and the MCS process at eight nozzle intervals, which is a common divisor of the nozzle number 128 of the overlap portions and the nozzle number 16 of the offset portions.

As described above, according to the second embodiment, in the execution of the HS process, the MCS process, or both, the image corresponding to the nozzle area having a common divisor of the number of nozzles of the overlapped portions and the number of nozzles of the offset portions Let data be the processing block. Accordingly, the boundaries of the nozzle regions corresponding to the input image data of the processing block are set to coincide with the boundaries of the overlapping portions and the non-overlap portions. For this reason, also in this embodiment, the nozzle which belongs to overlap parts and the nozzle which belongs to a non-overlap part do not mix in one process block, and the influence by a non-overlap part with respect to an overlap part is eliminated. For this reason, the effect of reducing the color difference which arises due to manufacturing variation can be increased. In addition, in this second embodiment, since the processing is carried out in a plurality of nozzles as in the first embodiment described above, the processing speed of the HS processing and the MCS processing can be greatly improved as compared with the case where the processing is performed for each nozzle. Can be. In addition, the memory capacity required for the processing can also be reduced.

Third Embodiment

Next, a third embodiment of the present invention will be described.

In the above-described first and second embodiments, an example of setting one processing block for HS processing and MCS processing of image data corresponding to nozzles of a print head has been described. In contrast, in the third embodiment, a plurality of different processing blocks are set as processing blocks of image data corresponding to nozzles of the print head.

Here, the print heads of each color shown in Fig. 4A are designed in such a way that the number of nozzles of each chip is 512 and the number of nozzles of the overlapping portion is 128. In the third embodiment, the HS and MCS processes are performed on the overlapping portions at eight nozzle intervals, which is a divisor of the number of nozzles 128. Further, for the non-overlap portion, 16 nozzles are set as the nozzle area, where the 16 nozzles are 384 nozzles of the non-overlap portions of the chips located at the ends of the print head and non-overlap portions of the chips not located at the ends. Is a common factor of 256 nozzles. Therefore, the HS process and the MCS process are executed at image data intervals corresponding to these nozzle areas. According to this, as in the first embodiment, the processing block can switch in response to the switching between the processing of the image printed by the overlapping portions and the processing of the image printed by the non-overlap portions, and the same as in the first embodiment. The effect of reducing color difference can be obtained.

In addition, when an error occurs in the number of nozzles with respect to the designed nozzle number of the overlap part due to the manufacturing variation, the effect of reducing color unevenness can be increased by adopting a smaller number of nozzles among the number of nozzle numbers of the overlap part. have. The same applies to the non-overlap portion. In the case where there is a manufacturing deviation, by adopting a smaller number of nozzles among common factors of non-overlap portions and making this the nozzle area corresponding to the processing block, the effect of reducing color nonuniformity can be increased.

As described above, in this third embodiment, two or more divisors of the number of nozzles in the overlapping portions and a separate number different from that are respectively designated nozzle regions, and images corresponding to the respective nozzle regions. HS processing and MCS processing are performed using data as a processing block. At this time, for at least the overlap parts, the number of nozzles of the overlap parts is set as the nozzle area, and the HS process and the MCS process are executed using the image data corresponding to the nozzle area as the processing block. According to this, the effect of reducing the color difference caused by the manufacturing variation can be increased. In addition to the configuration of the print head as described above, a plurality of different processing blocks may be set so that the processing blocks of the HS processing and the MCS processing can be switched in response to the switching between the overlapping portions and the non-overlap portions. At this time, for at least the overlap parts, it is necessary to set the number of nozzles, which is a divisor of the number of nozzles of the overlap parts, as the nozzle area, and the HS data and the MCS process are executed as image processing data corresponding to the nozzle area as processing blocks. In addition, as described in the first embodiment, overlap portions have a relatively large manufacturing variation compared to non-overlap portions. Therefore, as in the above-described example, it is preferable to make the number of nozzles corresponding to the processing block of the overlap parts smaller than the number of nozzles corresponding to the processing block of the non-overlap parts. As a result, the number of tables used for the HS processing and the MCS processing can be reduced for non-overlap portions having relatively small variations, and the increase in memory and processing time can be suppressed.

<Fourth Embodiment>

In the first to third embodiments, in at least the HS processing or MCS processing of the image data corresponding to the nozzles of the overlapping portions, the image data corresponding to the nozzle area having the nozzle number which is a divisor of the number of nozzles of the overlapping portions is processed. The example of setting as a block was illustrated. In contrast, in the fourth embodiment, when setting nozzle areas corresponding to the processing block, nozzle areas having a plurality of nozzles of different nozzle numbers are set without using a divisor of the number of nozzles of the overlapping part.

Here, the print head of Fig. 4A is designed in such a way that the number of nozzles of each chip is 512 and the number of nozzles of the overlapping portion is 128. With respect to the overlapping portions of the print head, HS processing and MCS processing are performed by setting the nozzle numbers that add up to the same number as the nozzle number 128 of the overlapping portion, for example, 8 processing blocks of 7 nozzles and 8 processing blocks of 9 nozzles. do. On the other hand, for the non-overlap portions, HS processing and MCS processing are executed at image data intervals corresponding to the nozzle area having 384 nozzles of the non-overlap portions and 16 nozzles, which is a common divisor of 256 nozzles. Accordingly, similarly to the first embodiment, the processing block of the image data can also be switched in response to the switching between the image processing printed by the overlapping portions and the image processing printed by the non-overlapping portions.

In addition, with regard to the non-overlap portions, as in the above-described overlap portions, a plurality of nozzles having different nozzle numbers in which the total number of nozzles matches the number of nozzles in the non-overlap portion can be used as the nozzle area, and image data corresponding to each nozzle area. Can be a processing block. If there is an error in the number of nozzles with respect to the designed number of nozzles due to the manufacturing deviation, nozzle areas including a plurality of nozzles different from the above-described example can be set, and image data corresponding thereto are set as processing blocks. Note that you can.

As described above, the overlap portions are subjected to image processing of the overlap portions by using a plurality of processing blocks having different nozzle numbers. Here, by arranging processing blocks corresponding to different numbers of nozzles so that the combined number of nozzles of each processing block matches the number of nozzles of the overlap portion, the effect of reducing color unevenness caused by variation in manufacturing can be increased. have.

<Fifth Embodiment>

Next, a fifth embodiment of the present invention will be described.

In the first to fourth embodiments, the case of switching the HS block of the image data and the processing block of the MCS process in response to the switching between the overlap portions and the non-overlap portions has been described as an example. In contrast, the fifth embodiment adopts a configuration in which switching between overlap portions and non-overlap portions does not coincide with switching of processing blocks.

Here, the print heads are print heads as shown in Fig. 4A, and the number of nozzles of each chip is 512, and the number of nozzles of the overlap portion is designed to be 128. In this case, in this embodiment, processing blocks of image data corresponding to the overlap portions are set as shown in FIG.

13 is a diagram showing an example of setting of a processing block in the present embodiment. In the figure, the numerical values in the boxes represent the number of nozzles of the processing blocks. C_A0 sets 23 processing blocks of 16 nozzles each, and C_T sets 14 processing blocks of 9 nozzles. Then, one processing block of 17 nozzles is set to include the boundary between C_A0 and C_T. Further, in C_T and C_A1, one processing block of 17 nozzles is separately set so as to include the boundary between C_T and C_A1, and six processing blocks of 16 nozzles are set in C_A1. In C_T and C_A2, one processing block of 17 nozzles is separately set so as to include the boundary between C_T and C_A2, and 23 processing blocks of 16 nozzles are set in C_A2, respectively.

It is noted that due to the manufacturing deviation, when there is an error in the number of nozzles with respect to the designed number of nozzles in the overlap portion, nozzle numbers different from the above example can be appropriately adopted as the processing blocks.

As described above, in the fifth embodiment, the overlap portion and the non-overlap portion exist in one processing block. For this reason, with respect to the correction of the non-overlap portions, there are influences of the overlap portions with relatively large manufacturing variations, which may cause color differences such as color and density unevenness. However, in this fifth embodiment, since values close to the nozzle numbers of the other embodiments described above are used as the processing blocks, the color difference caused by the presence of the overlap portion and the non-overlap portion in one processing block is visually visible. Hard to see Therefore, also in this fifth embodiment, by correcting the image data in each processing block, it is possible to reduce the color difference caused by the manufacturing deviation.

In the above first to fifth embodiments, the case of performing the HS process and the MCS process has been described, but the contents of each process are only examples, and the present invention can be applied to other processes for realizing color difference reduction. Note that there is. In addition, the MCS process described an example of correcting RGB values of image data to other RGB values, but the present invention also includes methods of correcting RGB values to CMYK values and methods of correcting CMYK values to other CMYK values. do.

Although the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

100: printer
315: head controller
317: scanner controller
401: input unit
402: image processing unit
403: input color conversion processing unit
404: MCS Processing Unit
405: ink color conversion processing unit
406: HS processing unit
407: TRC processing unit
408 quantization processing unit

Claims (11)

By using one or more print heads provided with a plurality of chips each having one or more nozzle arrays including a plurality of nozzles for ejecting ink, the ink is ejected from the nozzles based on print data generated in response to input image data. An inkjet printing device that prints images on print media,
The nozzle array of the chip has an overlap portion and a non-overlap portion,
A print area printed by the overlapping portion of the nozzle array of the chip overlaps the print area printed by the overlapping portion of the nozzle array of the chip proximate to the chip,
The print area printed by the non-overlap portion of the nozzle array of the chip does not overlap the print area printed by the non-overlap portion of the nozzle array of the chip proximate to the chip,
The inkjet printing device,
Set the input image data corresponding to the nozzle area defined in the nozzle array along the array direction of the nozzles and respectively constituted by a plurality of nozzles as a processing block, and set the input image data according to the parameters determined for each of the processing blocks. Including a correction unit for correcting,
And the nozzle area corresponding to the input image data of the processing block is determined according to a position of a boundary between the overlap portion and the non-overlap portion in the print head. The method of claim 1,
And the processing block is image data corresponding to a nozzle area composed of a predetermined number of nozzles. The method of claim 2,
And the processing block is image data corresponding to a nozzle area including a nozzle number including the number of nozzles of the non-overlap portion and a common number of nozzles of the overlap portion. The method of claim 2,
At least two of the plurality of print heads are arranged so that the overlap portions provided on each of them are not overlapped in a direction orthogonal to the arrangement direction of the nozzles, and the processing block is at least two arranged so that the overlap portions do not overlap. An inkjet printing apparatus according to the present invention, which is image data corresponding to a nozzle area including a nozzle number disposed between the overlap portion of the print head and two or more nozzle numbers, which is a common divisor of the number of nozzles of the overlap portion. The method of claim 1,
The processing block corresponds to an input image data corresponding to a nozzle area including two or more nozzles, which is a divisor of the number of nozzles of the overlap part, and a nozzle area including two or more nozzles, which is a divisor of the number of nozzles of the non-overlap part. An inkjet printing apparatus comprising input image data to be described. The method of claim 1,
The processing block corresponds to an input image data corresponding to a nozzle area including two or more nozzles, which is a divisor of the number of nozzles of the overlap part, and a nozzle area including two or more nozzles, which is a divisor of the number of nozzles of the non-overlap part. An inkjet printing apparatus comprising at least one of the image data. The method of claim 1,
And the correction unit performs correction based on ink discharge characteristics of the nozzles in the nozzle area corresponding to the processing block. The method of claim 1,
A color information acquisition unit for acquiring color information of an image formed on the print medium by the print head in each of the processing blocks;
And a parameter generating unit that generates a parameter corresponding to the processing block by using the color information acquired by the color information obtaining unit. By using one or more print heads provided with a plurality of chips each having one or more nozzle arrays including a plurality of nozzles for ejecting ink, the ink is ejected from the nozzles based on print data generated in response to input image data. Inkjet printing method to print an image on print media,
The nozzle array of the chip has an overlap portion and a non-overlap portion,
A print area printed by the overlapping portion of the nozzle array of the chip overlaps the print area printed by the overlapping portion of the nozzle array of the chip proximate to the chip,
The print area printed by the non-overlap portion of the nozzle array of the chip does not overlap the print area printed by the non-overlap portion of the nozzle array of the chip proximate to the chip,
The inkjet printing method,
A setting step of setting, as a processing block, input image data corresponding to a nozzle region defined in the nozzle array along the array direction of the nozzles and composed of a plurality of nozzles;
A correction step of correcting the input image data according to a parameter determined for each of the processing blocks by the setting step,
And the setting step determines the nozzle area corresponding to the input image data of the processing block according to the position of the boundary of the overlap portion and the non-overlap portion in the print head. An image processing apparatus for processing input image data to perform printing using one or more print heads provided with a plurality of chips each having one or more nozzle arrays including a plurality of nozzles for ejecting ink,
The nozzle array of the chip has an overlap portion and a non-overlap portion,
A print area printed by the overlapping portion of the nozzle array of the chip overlaps the print area printed by the overlapping portion of the nozzle array of the chip proximate to the chip,
The print area printed by the non-overlap portion of the nozzle array of the chip does not overlap the print area printed by the non-overlap portion of the nozzle array of the chip proximate to the chip,
The image processing apparatus,
Set the input image data corresponding to the nozzle area defined in the nozzle array along the array direction of the nozzles and respectively constituted by a plurality of nozzles as a processing block, and set the input image data according to the parameters determined for each of the processing blocks. Including a correction unit for correcting,
And the nozzle area corresponding to the input image data of the processing block is determined according to a position of a boundary between the overlap portion and the non-overlap portion in the print head. An image processing method for processing input image data for printing using one or more print heads provided with a plurality of chips each having one or more nozzle arrays including a plurality of nozzles for ejecting ink,
The nozzle array of the chip has an overlap portion and a non-overlap portion,
A print area printed by the overlapping portion of the nozzle array of the chip overlaps the print area printed by the overlapping portion of the nozzle array of the chip proximate to the chip,
The print area printed by the non-overlap portion of the nozzle array of the chip does not overlap the print area printed by the non-overlap portion of the nozzle array of the chip proximate to the chip,
The image processing method,
A setting step of setting, as a processing block, input image data corresponding to a nozzle area defined in the nozzle array along the array direction of the nozzles and composed of a plurality of nozzles, respectively;
A correction step of correcting the input image data according to a parameter determined for each of the processing blocks by the setting step,
And the setting step determines the nozzle area corresponding to the input image data of the processing block according to the position of the boundary of the overlap portion and the non-overlap portion in the print head.

Images